1. Field of the Invention
The present invention relates to an image pickup apparatus.
2. Description of the Related Art
In these days, there is provided an image pickup apparatus capable of capturing a still image while a moving image is being captured.
However, various capturing parameters such as time of exposure, resolution, ISO sensitivity, white balance adjustment, gamma correction are different between the moving image capturing and the still image capturing. Accordingly, at present, in order to capture the still image while the moving image is being captured, such processing is performed that the moving image capturing (recording of moving image frames) is suspended until the still image capturing is completed, and is restarted after completion of the still image capturing.
Therefore, Japanese Patent Application Laid-Open No. 2001-111934 discusses a technique of interpolating a plurality of moving image frames for the period that is suspended due to still image capturing. In the technique, the plurality of moving image frames are interpolated with interpolation frames generated from still image data acquired from the still image capturing and a preceding and a succeeding frames of the moving image frames that are lost due to the still image capturing. Further, there is provided a known image pickup apparatus capable of interpolating a plurality of moving image frames for the period suspended due to still image capturing with interpolation frames generated from black image data.
On the other hand, in recent years, as a compression coding standard of a moving image, increasing attention has been given to the Moving Picture Experts Group Phase 4 Advanced Visual Communication H.264 (MPEG-4 AVC/H.264). MPEG-4 AVC/H.264 realizes a compression rate higher than that in the past compression method such as the Moving Picture Experts Group 2 (MPEG-2), and has been employed as a compression method for the moving image data of image pickup apparatuses. Particularly, in MPEG-4 AVC/H.264, an instantaneous decoding refresh (IDR) frame is newly defined.
The IDR frame is an intra-frame (I-frame) encoded based only on intra-frame information. In MPEG-4 AVC/H.264, a predicted frame (P-frame) and a bi-directional predicted frame (B-frame) generated by encoding succeeding inter-frames of the IDR frame, are not allowed to refer to the preceding frame of the IDR frame.
Further, in MPEG-4 AVC/H.264, an IDR frame identifier (idr_pic_id) is assigned to each of the IDR frames, and it is defined that different IDR frame identifiers (idr_pic_id) should be assigned to the IDR frames that are adjacent to each other (ISO/IEC14496-10).
As discussed in Japanese Patent Application Laid-Open No. 2001-111934, in a case where the moving image frames corresponding to the period of still image capturing are interpolated with interpolation frames generated from still image data and predetermined interpolation frames, the interpolation is performed by inserting the same frame into the moving image frames more than once.
However, as a compression method for moving image data, for example, as in the case of MPEG-4 AVC/H.264, a compression method with a limiting condition such as “different IDR frame identifiers (idr_pic_id) should be assigned to the IDR frames adjacent to each other” is employed. In this case, employing such an interpolation method causes a problem in that the same IDR frame identifier (idr_pic_id) may be assigned to the IDR frames adjacent to each other in an interpolation frame section.